The Food & Drug Administration (FDA) and other worldwide regulatory agencies require medical device manufacturers to submit clinical and in vitro test data before commercial approval of prosthetic devices. As a part of this action, these devices are typically tested to 400,000,000 cycles simulating 10 years of life in the human body at an average heart rate of 80 beats per minute. Prosthetic testing apparatus and methods, such as those outlined by Vilendrer in U.S. Pat. No. 5,670,708 and Conti in U.S. Pat. No. 4,972,721, require significant capital investment and, in the case of the system outlined in U.S. Pat. No. 4,972,721, offer limited operating frequencies and measurement capabilities. Additionally, these test systems are typically built to order based on specific target prosthetic device sizes and configurations, limiting testing flexibility. Furthermore, current systems employ a flexible metallic bellows or conventional piston and cylinder as drive members to provide the pressure actuation.
These traditional fluid drive technologies have several shortcomings. For example, flexible metallic bellows are not ideal because they require high forces to operate and resonate at specific frequencies, necessitating the use of larger driving systems and limiting the available test speeds. Also, piston and cylinder arrangements employ traditional seals which are subject to friction and thus have severely limited life in high cycle applications. Additionally, known single drive systems create standing waves along the length of the prosthetic devices being tested, which is not a natural pressure waveform found in the human body. Therefore, the test sample is not excited in a clinically relevant manner.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the claimed invention is to be bound.